hwpoison, hugetlb: lock_page/unlock_page does not match for handling a free hugepage

For handling a free hugepage in memory failure, the race will happen if
another thread hwpoisoned this hugepage concurrently.  So we need to
check PageHWPoison instead of !PageHWPoison.

If hwpoison_filter(p) returns true or a race happens, then we need to
unlock_page(hpage).

Signed-off-by: Chen Yucong <slaoub@gmail.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: <stable@vger.kernel.org>	[2.6.36+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 35ef28acf137c0ab76393ede3dbc1c3d820f5c37..dbf8922216ade6c88bbf1855cca60e881abc6b47 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1081,15 +1081,16 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
                        return 0;
                } else if (PageHuge(hpage)) {
                        /*
-                        * Check "just unpoisoned", "filter hit", and
-                        * "race with other subpage."
+                        * Check "filter hit" and "race with other subpage."
                         */
                        lock_page(hpage);
-                       if (!PageHWPoison(hpage)
-                           || (hwpoison_filter(p) && TestClearPageHWPoison(p))
-                           || (p != hpage && TestSetPageHWPoison(hpage))) {
-                               atomic_long_sub(nr_pages, &num_poisoned_pages);
-                               return 0;
+                       if (PageHWPoison(hpage)) {
+                               if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
+                                   || (p != hpage && TestSetPageHWPoison(hpage))) {
+                                       atomic_long_sub(nr_pages, &num_poisoned_pages);
+                                       unlock_page(hpage);
+                                       return 0;
+                               }
                        }
                        set_page_hwpoison_huge_page(hpage);
                        res = dequeue_hwpoisoned_huge_page(hpage);